Wireless communication system, base station, mobile station, base station control program, and mobile station control program

ABSTRACT

A base station which includes a transmission section that is configured to transmit, to a mobile station, first information indicating first control information for controlling a number of transmission antennas of the mobile station for retransmitting transmission data with at least second information indicating a retransmission request and third information indicating second control information for controlling retransmission power for retransmitting the transmission data. The base station also includes a radio section configured to receive, from the mobile station, the transmission data.

This application is a Divisional of co-pending application Ser. No.13/377,474 filed on Dec. 13, 2011, and for which priority is claimedunder 35 U.S.C. §120, application Ser. No. 13/377,474 is the nationalphase of PCT International Application No. PCT/JP2010/057260 filed onApr. 23, 2010 under 35 U.S.C. §371, which claims the benefit of priorityof JP2009-141141 filed Jun. 12, 2009. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a wireless communication system, a basestation, a mobile station, a base station control program, and a mobilestation control program, each of which performs retransmissionprocessing in wireless communication.

BACKGROUND ART

The LTE (Long Term Evolution) system, which is the 3.9th generationwireless communication system for a mobile phone, employs HARQ (HybridAutomatic Repeat Request) which is a retransmission control method ofperforming error detection of a transmission packet between a basestation and a mobile station and transmitting a packet having caused anerror again. This retransmission control checks a packet error by usingCRC (Cyclic Redundancy Check) added to the transmission packet andtransmits NACK (Negative Acknowledgement) which is a retransmissionrequest signal when the received packet has not been able to be decodedcorrectly. Furthermore, ACK (Acknowledgement) which is a transmissionacknowledgement signal is transmitted when the transmitted packet hasbeen received correctly (refer to Non-patent document 1).

The retransmission control includes Non-adaptive ARQ and Adaptive ARQ.While Non-adaptive ARQ transmits data in retransmission by the sametransmission method as that at the time of initial transmission,Adaptive ARQ transmits retransmission data different from that in theinitial transmission by changing a parameter such as a modulationscheme, a coding rate, a puncture pattern, a frequency band width to beused, transmission power (refer to Patent document 1). Furthermore,there is proposed a method of using a plurality of antennas at the timeof the retransmission, such as STTD (Space Time Transmit Diversity) andMIMO (Multiple-Input Multiple-Output) which are transmission diversitymethods (refer to Patent document 1).

PRIOR ART DOCUMENT Patent Document

Patent document 1: Japanese Patent Application Laid-Open Publication No.2007-214824

Patent document 2: Pamphlet of International Publication No.

Non-Patent Document

Non-patent document 1: 3GPP TS 36.211 (V8.6.0) “Evolved UniversalTerrestrial Radio Access (E-UTRA) Physical Channels and Modulation”

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, the retransmission control by Adaptive ARQ has not beenexamined in consideration of a PH (Power Headroom) indicating atransmission power headroom, in a wireless communication system whichenables access methods having respective peak powers different from oneanother to be used in an uplink, such as Clustered DFT-S-OFDM (DynamicSpectrum Control (DSC), also called DFT-S-OFDM with SDC (SpectrumDivision Control)) and DFT-S-OFDM (Discrete Fourier Transform SpreadOrthogonal Frequency Division Multiplexing, also called SC-FDMA).Accordingly, in the retransmission using an access method requiring ahigh peak power, there is a problem in which a user without having roomfor PH such as a cell-edge user cannot further increase the transmissionpower and a base station cannot receive data correctly.

The present invention has been achieved in view of such a situation, andaims at providing a wireless communication system, a base station, amobile station, a base station control program, and a mobile stationcontrol program, which control an access method, a transmission power,an antenna to be used, and the number of antennas in consideration ofthe PH indicating a transmission power headroom.

Means for Solving the Problem

(1) For achieving the above object, the present invention employs thefollowing measures. That is, a wireless communication system of thepresent invention is configured with a base station and a mobile stationand performs wireless communication by selecting any one of a pluralityof access methods having respective peak powers different from oneanother, wherein, when retransmission occurs in the access method usedby the mobile station, the base station selects an access method havinga lower peak power than the access method and also instructs the mobilestation to perform the retransmission by increasing transmission power.

In this manner, when the retransmission occurs in the access method usedby the mobile station, the base station selects an access method havinga lower peak power than the access method and also instructs the mobilestation to perform the retransmission by increasing the transmissionpower, and thus the mobile station can avoid a transmission powershortage and perform the retransmission with a sufficient transmissionpower. This results in an improvement of a cell throughput.

(2) A wireless communication system of the present invention which isconfigured with a base station and a mobile station and in which themobile station performs data transmission to the base station byallocating a transmission signal converted into a frequency signal tocontiguous frequency bands or non-contiguous frequency bands dividedinto a predetermined number, wherein, when retransmission occurs in thedata transmission the mobile station has performed by allocating thetransmission signal converted into the frequency signal to thenon-contiguous frequency bands, the base station determines atransmission power headroom of the mobile station in the allocation ofthe transmission signal to the non-contiguous frequency bands, and, if aresult of the determination shows that there is not a transmission powerheadroom, the base station instructs the mobile station to allocate thetransmission signal to the contiguous frequency bands and to perform theretransmission by increasing transmission power.

In this manner, when the retransmission occurs in the data transmissionthe mobile station has performed by allocating the transmission signalconverted into the frequency signal to the non-contiguous frequencybands, the base station determines a transmission power headroom of themobile station in the allocation of the transmission signal to thenon-contiguous frequency bands, and, if a result of the determinationshows that there is not a transmission power headroom, instructs themobile station to allocate the transmission signal to the contiguousfrequency bands and to perform the retransmission by increasing thetransmission power, and thus it is possible to suppress the increase ofthe retransmission due to a shortage of the transmission power in themobile station and to improve the cell throughput.

(3) Furthermore, in the wireless communication system of the presentinvention, the mobile station performs the retransmission by increasingthe transmission power by an amount corresponding to a transmissionpower headroom generated by the allocation of the transmission signal tothe contiguous frequency bands.

In this manner, the mobile station performs the retransmission byincreasing the transmission power by an amount corresponding to atransmission power headroom generated by the allocation of thetransmission signal to the contiguous frequency bands, and thus themobile station can avoid a transmission power shortage and perform theretransmission with a sufficient transmission power. This results in theimprovement of the cell throughput.

(4) Furthermore, in the wireless communication system of the presentinvention, the mobile station allocates the transmission signal to thecontiguous frequency bands and also performs the retransmission byincreasing the transmission power by a predetermined amount.

In this manner, the mobile station allocates the transmission signal tothe contiguous frequency bands and also performs the retransmission byincreasing the transmission power by a predetermined amount, and thusthe base station needs not notify the mobile station of controlinformation of the transmission power at the time of the retransmissionand the mobile station can avoid a transmission power shortage andperform the retransmission with a sufficient transmission power. Thisresults in the improvement of the cell throughput.

(5) Furthermore, in the wireless communication system of the presentinvention, the mobile station has a plurality of antennas and the basestation instructs the mobile station to allocate the transmission signalto the contiguous frequency bands and to perform the retransmission byusing an antenna having a high channel gain among the plurality ofantennas included in the mobile station and by increasing thetransmission power.

In this manner, the mobile station includes a plurality of antennas andthe base station instructs the mobile station to allocate thetransmission signal to the contiguous frequency bands and to perform theretransmission by using an antenna having a high channel gain among theplurality of antennas included in the mobile station and by increasingthe transmission power, and thus the base station can suppress theincrease of the retransmission due to a shortage of the transmissionpower in the mobile station and improve the cell throughput by anantenna diversity effect.

(6) Furthermore, in the wireless communication system of the presentinvention, the base station determines an increase amount of thetransmission power based on a channel gain of the antenna to be used atthe time of the retransmission.

In this manner, the base station determines an increase amount of thetransmission power based on a channel gain of an antenna used at thetime of the retransmission, and thus the base station can set thetransmission power flexibly in accordance with the channel gain of theantenna used in the mobile station.

(7) Furthermore, in the wireless communication system, the mobilestation has a plurality of antennas, and the base station determines thenumber of antennas to be used at the time of the retransmission amongthe plurality of antennas included in the mobile station and instructsthe mobile station to allocate the transmission signal to the contiguousfrequency bands and to perform the retransmission by using a determinednumber of antennas and by increasing the transmission power.

In this manner, the mobile station has a plurality of antennas and thebase station determines the number of antennas to be used at the time ofthe retransmission among the plurality of antennas included in themobile station and instructs the mobile station to allocate thetransmission signal to the contiguous frequency bands and to perform theretransmission by using a determined number of antennas and byincreasing the transmission power, and thus the base station cansuppress the increase of the retransmission due to a shortage of thetransmission power in the mobile station and improve the cell throughputby the transmission diversity effect.

(8) Furthermore, in the wireless communication system of the presentinvention, the mobile station performs the retransmission by increasingthe transmission power larger than a total power at the time of initialtransmission by an amount corresponding to a transmission power headroomgenerated by the allocation of the transmission signal to the contiguousfrequency bands and by using a determined number of antennas.

In this manner, the mobile station performs the retransmission byincreasing the transmission power larger than a total power at the timeof the initial transmission by an amount corresponding to a transmissionpower headroom generated by the allocation of the transmission signal tothe contiguous frequency bands and by using a determined number ofantennas, and thus the mobile station can suppress the increase of theretransmission due to a shortage of the transmission power.

(9) A base station of the present invention is applied to a wirelesscommunication system which is configured with the base station and amobile station and in which the mobile station performs datatransmission to the base station by allocating a transmission signalconverted into a frequency signal to contiguous frequency bands ornon-contiguous frequency bands divided into a predetermined number,wherein, when retransmission occurs in the data transmission the mobilestation has performed by allocating the transmission signal convertedinto the frequency signal to the non-contiguous frequency bands, thebase station determines a transmission power headroom of the mobilestation in the allocation of the transmission signal to thenon-contiguous frequency bands, and, if a result of the determinationshows that there is not a transmission power headroom, the base stationinstructs the mobile station to allocate the transmission signal to thecontiguous frequency bands and to perform the retransmission byincreasing transmission power.

In this manner, when the retransmission occurs in the data transmissionthe mobile station has performed by allocating the transmission signalconverted into the frequency signal to the non-contiguous frequencybands, the base station determines a transmission power headroom of themobile station in the allocation of the transmission signal to thenon-contiguous frequency bands, and, if a result of the determinationshows that there is not a transmission power headroom, the base stationinstructs the mobile station to allocate the transmission signal to thecontiguous frequency bands and to perform the retransmission byincreasing the transmission power, and thus the base station cansuppress the increase of the retransmission due to a shortage of thetransmission power in the mobile station and can improve the cellthroughput.

(10) A mobile station of the present invention is applied to a wirelesscommunication system which is configured with a base station and themobile station and in which the mobile station performs datatransmission to the base station by allocating a transmission signalconverted into a frequency signal to contiguous frequency bands ornon-contiguous frequency bands divided into a predetermined number,wherein the mobile station performs retransmission to the base stationby increasing transmission power by an amount corresponding to atransmission power headroom generated by the allocation of thetransmission signal to the contiguous frequency bands.

In this manner, the mobile station performs the retransmission to thebase station by increasing the transmission power by an amountcorresponding to a transmission power headroom generated by theallocation of the transmission signal to the contiguous frequency bands,and thus the mobile station can avoid a shortage of the transmissionpower and perform the retransmission with a sufficient transmissionpower. This results in the improvement of the cell throughput.

(11) A base station control program of the present invention is appliedto a wireless communication system which is configured with a basestation and a mobile station and in which the mobile station performsdata transmission to the base station by allocating a transmissionsignal converted into a frequency signal to contiguous frequency bandsor non-contiguous frequency bands divided into a predetermined number,wherein, when retransmission occurs in the data transmission the mobilestation has performed by allocating the transmission signal convertedinto the frequency signal to the non-contiguous frequency bands, thebase station control program converts a series of processing steps intoa command in a manner a computer can read and execute the command, theseries of processing steps including processing of determining atransmission power headroom of the mobile station in the allocation ofthe transmission signal to the non-contiguous frequency bands, and, if aresult of the determination shows that there is not a transmission powerheadroom, includes processing of instructing the mobile station toallocate the transmission signal to the contiguous frequency bands andto perform the retransmission by increasing transmission power.

In this manner, when the retransmission occurs in the data transmissionthe mobile station has performed by allocating the transmission signalconverted into the frequency signal to the non-contiguous frequencybands, the series of processing, which includes the processing ofdetermining a transmission power headroom of the mobile station in theallocation of the transmission signal to the non-contiguous frequencybands, and, if a result of the determination shows that there is not atransmission power headroom, the processing of instructing the mobilestation to allocate the transmission signal to contiguous frequencybands and to perform the retransmission by increasing the transmissionpower, is converted into a command in a manner a computer can read andexecute the command, and thus it is possible to suppress the increase ofthe retransmission due to a shortage of the transmission power in themobile station and to improve the cell throughput.

(12) A mobile station control program of the present invention isapplied to a wireless communication system which is configured with abase station and a mobile station and in which the mobile stationperforms data transmission to the base station by allocating atransmission signal converted into a frequency signal to contiguousfrequency bands or non-contiguous frequency bands divided into apredetermined number, wherein the mobile station program convertsprocessing into a command in a manner a computer can read and executethe command, the processing performing retransmission to the basestation by increasing transmission power by an amount corresponding to atransmission power headroom generated by the allocation of thetransmission signal to the contiguous frequency bands.

In this manner, the processing, which performs the retransmission to thebase station by increasing transmission power by an amount correspondingto a transmission power headroom generated by the allocation of thetransmission signal to the contiguous frequency bands, is converted intoa command in a manner a computer can read and execute the command, andthus it is possible to suppress the increase of the retransmission dueto a shortage of the transmission power in the mobile station and toimprove the cell throughput.

Advantage of the Invention

By applying the present invention, it is possible to avoid a situationin which transmission power runs short in retransmission and data cannotbe transmitted correctly, even in the case of a user present at a celledge, and it is possible to improve cell throughput.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an outline configuration exampleof a mobile station according to a first embodiment.

FIG. 2 is a block diagram illustrating an outline configuration exampleof a base station according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating retransmission processing of a firstembodiment.

FIG. 4 is a diagram illustrating transmission power when a mobilestation transmits data using non-contiguous frequency bands.

FIG. 5 is a diagram illustrating transmission power when a mobilestation transmits data by increasing the transmission power through theuse of contiguous frequency bands.

FIG. 6 is a flowchart of a determination method for control informationabase station transmits at the time of a retransmission request of afirst embodiment.

FIG. 7 is a block diagram illustrating an outline configuration exampleof a mobile station according to a second embodiment.

FIG. 8 is a diagram illustrating retransmission processing of a secondembodiment.

FIG. 9 is a block diagram illustrating an outline configuration exampleof a mobile station according to a third embodiment.

FIG. 10 is a diagram illustrating retransmission processing of a thirdembodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

The standardization of the LTE system has been almost completed andrecently the standardization of LTE-A (also called LTE-Advanced, IMT-A,or the like), which is the fourth generation wireless communicationsystem developed further from the LTE system, has been started.

An uplink (communication from a mobile station to a base station) inLTE-A is required to have a higher peak data rate than that in LTE andto have an improved spectrum efficiency. Accordingly, an improvement ofa throughput by introducing a new access method and an improvement ofthe peak data rate by using a multiple antenna technique are beingstudied.

As an access method in the LTE-A system uplink, there is proposedClustered DFT-S-OFDM which places emphasis on backward compatibility,supports DFT-S-OFDM, and further can improve the throughput. ClusteredDFT-S-OFDM is an access method which selects a frequency having a highchannel gain from an available band and allocatesspectranon-contiguously, and thus Clustered DFT-S-OFDM can obtain a highfrequency diversity effect, while requiring a higher peak power thanDFT-S-OFDM, and can improve the cell throughput.

Furthermore, while an uplink in LTE system does not use a plurality ofantennas at the same time, in the LTE-A system, there is being examineda method of improving the spectrum efficiency and coverage by using MIMO(Multiple-Input Multiple-Output) multiple transmission and transmissiondiversity which use a plurality of transmission antennas at the sametime.

Hereinafter, embodiments of the present invention will be explained withreference to the drawings. While, in the following embodiments,explanation will be made only for a case in which single carriertransmissions having respective peak powers different from one anotherare available in a mobile station of a transmission apparatus,substantially the same retransmission method which is based on atransmission power headroom is included in the present invention alsofor a case in which single carrier transmission and multi-carriertransmission which have respective peak powers different from each otherare available.

FIG. 1 is a block diagram illustrating an outline configuration exampleof a mobile station according to a first embodiment. The mobile stationis provided with a buffer section 100, a coding section 101, amodulation section 102, a DFT section 103, a transmission dataallocation section 104, an IDFT section 105, a reference signalgeneration section 106, a reference signal insertion section 107, a CPinsertion section 108, a radio section 109, a PA section 110, atransmission antenna 111, a transmission power headroom calculationsection 112, a control information transmission section 113, a controlinformation reception processing section 114, a reception antenna 115,and a retransmission control section 116.

The mobile station receives control information including frequencyallocation information, notification of which has been received fromabase station of a reception apparatus and, after having performed datatransmission according to the frequency allocation information, receivesa transmission acknowledgement signal, notification of which is to bereceived from the base station with the reception antenna 115. Thistransmission acknowledgement signal shows whether or not the basestation has been able to decode data transmitted from the mobile stationcorrectly, and exhibits ACK when the base station has been able todecode the data correctly and exhibits NACK when the base station hasnot been able to decode the data correctly. When a transmission methoddifferent from that of initial data transmission is to be used at thetime of retransmission, the mobile station also receives controlinformation such as a frequency allocation method and a transmissionpower. A signal received by the reception antenna 115 is input to thecontrol information reception processing section 114.

The control information reception processing section 114 obtains thetransmission acknowledgement signal and the frequency allocationinformation from the reception signal. The obtained transmissionacknowledgement signal is input to the retransmission control section116, and, in contrast, the frequency allocation information of thecontrol information is input to the transmission data allocation section104 and the transmission power information is input to the PA (PowerAmplifier) section 110.

The retransmission control section 116 inputs transmission data, whichhas been input to the buffer section 100, to the coding section 101 whenthe input transmission acknowledgement signal exhibits ACK, and inputstransmission data, which is stored in the buffer and which the basestation has not been able to receive correctly, to the coding section101 when the input transmission acknowledgement signal exhibits NACK.

The transmission data input to the coding section 101 is converted intocode bits provided with a error correcting code and is modulated into amodulation symbol such as QPSK (Quadrature Phase Shift Keying) and 16QAM (16 Quadrature Amplitude Modulation) in the modulation section 102.The modulation symbols are converted into a frequency domain signal inthe DFT section 103, and the transmission data allocation section 104allocates the frequency signal based on the frequency allocationinformation, notification of which has been received from the basestation. The IDFT (Inverse Discrete Fourier Transform) section 105converts the frequency signals into a time domain signal. A signalgenerated in the reference signal generation section 106 is inserted inthe reference signal insertion section 107. While the reference signalis inserted into the time domain signal in the present embodiment, thereference signal may be frequency-multiplied before the frequency signalis converted into the time domain signal in the IDFT section 105. The CP(Cyclic Prefix) insertion section 108 adds a CP to the time signal, andthe time signal is up-converted into a radio frequency by the radiosection 109 and transmitted from the transmission antenna 111 afterhaving been amplified in the PA section 110 so as to have a transmissionpower, notification of which has been received from the base station.

Furthermore, a transmission power headroom calculated by thetransmission power headroom calculation section 112 is transmittedperiodically to the base station via the control informationtransmission section 113.

While, in the present embodiment, the retransmission is configured tostart from the coding of the transmission data, the coding may not beperformed again and the coded data may be stored, when a coding method,a coding rate, a constraint length, a puncture pattern, and the like tobe applied are not changed. Similarly, when a modulation scheme to beapplied is not changed in the modulation section, the frequency domainsignal obtained by DFT may be stored.

FIG. 2 is a block diagram illustrating an outline example of a basestation according to an embodiment of the present invention. The basestation is provided with a reception antenna 201, a radio section 202, aCP removal section 203, a reference signal separation section 204, a DFTsection 205, a transmission data extraction section 206, a channelcompensation section 207, an IDFT section 208, a demodulation section209, a decoding section 210, a cyclic redundancy check section 211, achannel estimation section 213, a frequency allocation decision section214, control information generation section 215, a control informationtransmission section 216, a buffer section 217, a transmissionacknowledgement signal transmission section 218, a transmission antenna219, and a control information buffer section 220.

The reception antenna 201 receives data or control informationtransmitted from the mobile station. When the data is received, theradio section 202 down-converts a signal received by the receptionantenna 201 into a base band frequency, the CP removal section 203removes the cyclic prefix, and the reference signal separation section204 separates the reference signal. The separated reference signal isinput to the channel estimation section 213 and a frequency response ofa channel is estimated from the reference signal. The estimated channelinformation is input to the channel compensation section 207 and thefrequency allocation decision section 214.

In contrast, the signal (which has been) separated from the referencesignal is converted into a frequency domain signal by the DFT section205 and the transmission data extraction section 206 extracts thetransmitted data from frequencies in which the data is allocated, basedon the frequency allocation information stored in the buffer section217. The channel compensation section 207 performs processing ofcompensating a radio channel distortion such as multiplication of aminimum mean square error (MMSE) weight through the use of the frequencyresponse estimated by the channel estimation section 213, and the IDFTsection 208 converts the data into a time domain signal. The obtainedtime domain signal is broken down from the modulation symbol intoreception code bits by the demodulation section 209 and is subjected toerror correction decoding by the decoding section 210. The cyclicredundancy check section 211 determines whether or not the decoded datahas been received correctly by using the CRC added to the transmissiondata.

Furthermore, when the control information is received, the controlinformation can be obtained by the same reception processing, and when aPH is received as the control information, the PH is stored in thecontrol information buffer section 220 to be used for retransmissioncontrol.

When the cyclic redundancy check section 211 has determined that thereception data is correct, ACK is transmitted via the transmissionacknowledgement signal transmission section 218. When an error has beendetected in the reception data, NACK is transmitted via the transmissionacknowledgement signal transmission section 218. Furthermore, the PHinformation stored in the control information buffer section 220 isinput to the frequency allocation decision section 214.

The frequency allocation decision section 214 determines frequencyallocation based on the input channel information and the controlinformation such as the PH, and inputs the frequency allocation to thebuffer section 217 and the control information generation section 215.For the frequency allocation, it is determined based on the PHindicating a transmission power headroom whether the contiguousallocation or the non-contiguous allocation is to be used, and whenthere is not a transmission power headroom, the contiguous frequencyallocation is used. Furthermore, frequency bands to be allocated aredetermined based on the channel information estimated in the channelestimation section 213. The control information generation section 215generates the control information and the control information istransmitted from the transmission antenna 219 via the controlinformation transmission section 216.

First Embodiment

A first embodiment is related to a retransmission method in which themobile station performs the data transmission by using ClusteredDFT-S-OFDM and the base station detects an error from a decoding resultof the reception data by the CRC. There will be explained an example ofswitching to DFT-S-OFDM when there is not a transmission power headroomand an example of increasing the transmission power by an amount ofmargin for back-off, generated by the switching. While the number of thetransmission antennas 111 of the mobile station is set to be one, thepresent embodiment can be applied when one antenna 111 is used even ifthe mobile station includes a plurality of antennas 111.

FIG. 3 is a diagram illustrating retransmission processing of the firstembodiment. The mobile station 301 periodically notifies the basestation 303 of a PH as the control information (Step S1). In contrast,the base station 303 determines the transmission power of the mobilestation 301 in consideration of interference with a mobile station 301within the same cell as that of the PH, notification of which has beenreceived from the mobile station 301, and notifies the mobile station301 thereof (Step S2).

FIG. 4 is a diagram illustrating transmission power when the mobilestation 301 transmits data by using non-contiguous frequency bands. InFIG. 3, when the mobile station 301 performs data transmission, the basestation 303 transmits control information, which includes theinformation of allocating non-contiguous frequency, to the mobilestation 301 (Step S3). The mobile station 301 transmits data by usingthe non-contiguous frequency bands as shown in FIG. 4 based on to thereceived control information (Step S4).

FIG. 5 is a diagram illustrating the transmission power when the mobilestation 301 transmits data by increasing the transmission power throughthe use of the contiguous frequency bands. In FIG. 3, when the basestation 303 has detected an error by the CRC in the data obtained by thedecoding of the reception signal, the base station 303 transmits NACKwhich is a retransmission request (Step S5). Furthermore, when there isa transmission power headroom smaller than the PH, of which the mobilestation 301 notifies the base station 303 periodically, the base station303 determines the allocation of the contiguous frequency bands which isa transmission method having a lower peak power. By the allocation ofthe contiguous bands, a required back-off amount becomes small, thetransmission power headroom becomes sufficient, and thus the increase inthe transmission power becomes possible as shown in FIG. 5.

In FIG. 3, the base station 303 notifies the mobile station 301 of thefrequency allocation information and the transmission power as controlinformation in Step S5. The mobile station 301 performs theretransmission based on the received control information (Step S6), andthe base station 303 transmits ACK in return if the base station hasbeen able to receive the data correctly (Step S7).

FIG. 6 is a flowchart of a determination method for control informationthe base station 303 transmits at the time of the retransmission requestof the first embodiment. The base station 303 receives the datatransmitted through the use of the non-contiguous frequency (Step S101).The base station 303 decodes the received data and determines whether ornot the decoding has been performed correctly by detecting an error bythe CRC (Step S102). When the decoding has succeeded, the base station303 notifies the mobile station 301 of ACK as the acknowledgement signal(Step S106).

When the decoding has failed, the base station 303 confirms whether ornot there is a transmission power headroom, based on the PH,notification of which has been received from the mobile station 301(Step S103). When there is a transmission power headroom, the basestation 303 generates the control information of allocating thenon-contiguous frequency (Step S105). The allocation of thenon-contiguous frequency may be the same as that in the initial datatransmission or may be changed. Furthermore, since there is atransmission power headroom, the base station 303 may transmit thecontrol information of increasing the transmission power, to the mobilestation 301. When there is not a transmission power headroom, the basestation 303 generates the control information of the contiguousfrequency allocation and the transmission power (Step S104). The basestation 303 notifies the mobile station 301 of the generated controlinformation and NACK which is the transmission acknowledgement signal(Step S107).

By applying the present embodiment, it is possible to suppress theincrease of the retransmission due to a shortage of the transmissionpower and to improve the cell throughput, since the base station 303changes the transmission method of the retransmission in considerationof a transmission power headroom when the base station 303 has detectedan error in the transmission of the non-contiguous frequency bandsperformed by the mobile station 301 through the use of one transmissionantenna. While, in the present embodiment, the allocation is changed tothe contiguous frequency allocation when there is not a transmissionpower headroom and the contiguous frequency allocation is used whenthere is a transmission power headroom, multiple carriers may be usedwhen there is a transmission power headroom and the retransmission maybe performed by a single carrier when there is not a transmission powerheadroom. Furthermore, while the base station 303 is configured tonotify the mobile station 301 of the control information including thechange to the contiguous frequency allocation and the transmission powerat the time of the retransmission, a predetermined value may be used asthe transmission power at the time of the retransmission, if thetransmission power is smaller than an increased amount of thetransmission power headroom.

Second Embodiment

In a second embodiment, there will be explained an example in which,when the mobile station 301 performs data transmission by ClusteredDFT-S-OFDM, the mobile station 301 changes the bands to be allocated inconsideration of a transmission power headroom, increases thetransmission power by margin for the back-off, and switches to atransmission antenna 605 having a higher channel gain, at the time ofthe retransmission. While in the present invention, the number of thetransmission antennas 605 is set to be one in the initial transmission,a case in which the plurality of transmission antennas 605 is used canalso be applied.

FIG. 7 is a block diagram illustrating an outline configuration exampleof a mobile station according to the second embodiment. The mobilestation 301 has a plurality of antennas and, for the transmissionantenna 605, the mobile station 301 is provided with a buffer section600, a transmission signal generation section 601, an antennadetermination section 602, a radio section 603, a PA section 604, atransmission power headroom calculation section 606, a controlinformation transmission section 607, a control information receptionsection 608, a reception antenna 609, and a retransmission controlsection 610. For transmission antennas 605′ and 605″ excluding thetransmission antenna 605, the mobile station 301 similarly includesrespective radio sections 603′ and 603″ and respective PA sections 604′and 604″.

The mobile station 301 receives control information with the receptionantenna 609. The control information reception section 608 obtains thetransmission acknowledgement signal of ACK or NACK and the controlinformation indicating the frequency allocation information, theretransmission antenna information, the transmission power at the timeof the retransmission, and the like, from the received controlinformation.

The control information reception section 608 inputs the transmissionacknowledgement signal to the retransmission control section 610, inputsthe frequency allocation information to the transmission signalgeneration section 601, inputs the retransmission antenna information tothe antenna determination section 602, and inputs the transmission powerat the time of the retransmission to the PA section 604. Theretransmission control section 610 inputs transmission data input to thebuffer section 600, to the transmission signal generation section 601when the transmission acknowledgement signal exhibits ACK, and inputs,for retransmission, transmission data, which has not been able to bereceived correctly by the base station 303 and which is stored in thebuffer, to the transmission signal generation section 601 when thetransmission acknowledgement signal exhibits NACK. The transmissionsignal generation section 601 subjects the input transmission data tothe same processing as the processing from coding section 101 to the CPinsertion section 108 in FIG. 1, and inputs the transmission data to theantenna determination section 602. The antenna determination section 602selects a transmission antenna 605 for the retransmission which isindicated by the retransmission antenna information input from thecontrol information reception section 608, and inputs the transmissionsignal input from the transmission signal generation section 601 to theradio section 603 of the transmission antenna 605 for theretransmission.

Furthermore, the PA section 604 of the transmission antennas 605 to beused for the retransmission performs amplification based on thetransmission power information, notification of which has been receivedfrom the base station 303, and transmits the retransmission data fromthe transmission antenna 605 to be used for the retransmission.

The configuration of the base station 303 is the same as that of FIG. 2,and the channel estimation section 213 inputs the retransmission antennainformation and the channel information based on the plurality ofantenna channels to the frequency allocation decision section. Thefrequency allocation decision section 214 determines the bands to beallocated based on the channel information, and inputs the frequencyallocation information and the retransmission antenna information to thecontrol information generation section 215. The frequency allocationinformation and the retransmission antenna information are convertedinto control information data in the control information generationsection 215 and transmitted from the transmission antenna 219 via thecontrol information transmission section 216.

FIG. 8 is a diagram illustrating retransmission processing of the secondembodiment. The mobile station 301 periodically notifies the basestation 303 of a PH as the control information (Step S201). In contrast,the base station 303 determines the transmission power of the mobilestation 301 in consideration of interference with a mobile station 301within the same cell as that of the PH, notification of which has beenreceived, and notifies the mobile station 301 thereof (Step S202). Whenthe mobile station 301 performs data transmission, the base station 303transmits the control information, which includes the information ofallocating the non-contiguous frequency, to the mobile station 301 (StepS203). The mobile station 301 transmits data by using the non-contiguousfrequency bands based on the received control information (Step S204).The mobile station 301 performs the data transmission by using thenon-contiguous frequency, and the base station 303 detects an error inthe decoded result of the received data by the cyclic redundancy check.When the error has been detected and there is not a transmission powerheadroom in the PH, notification of which has been periodically receivedfrom the mobile station 301, the base station 303 allocates thecontiguous bands, designates a transmission antenna 605 having a highchannel gain, and performs retransmission request (Step S205). Sincethere is room for transmission power headroom, the transmission power atthe time the retransmission is increased in consideration of a receptionSINR (Signal to Interference and Noise power Ratio) which is a channelgain of the antenna used for the retransmission. The mobile station 301performs the retransmission based on the received control information(Step S206), and the base station 303 transmits ACK in return when thedata has been able to be received correctly (Step S207).

By applying the present embodiment, it is possible to suppress theincrease of the retransmission due to a shortage of the transmissionpower and to improve the cell throughput by the antenna diversityeffect, since the base station 303 changes the transmission method forthe retransmission and the transmission antenna 605 in consideration ofa transmission power headroom when the base station 303 has detected anerror in the transmission performed by the mobile station 301 throughthe use of the non-contiguous frequency bands.

Third Embodiment

In a third embodiment, there will be explained an example in which, whena mobile station 301 performs data transmission by Clustered DFT-S-OFDM,the mobile station 301 changes the bands to be allocated inconsideration of a transmission power headroom and increases thetransmission power by margin for the back-off, at the time of theretransmission, and switches the number of transmission antennas 905 tobe used for the retransmission. While in the present embodiment, thenumber of the transmission antennas 905 in the mobile station 301 is setto be two at the time of the retransmission, even three or moretransmission antennas 905 used for the retransmission can be applied.Furthermore, while in the present embodiment, the number of transmissionantennas 905 for the initial transmission is set to be one, the use of aplurality of transmission antennas 905 can also be applied.

FIG. 9 is a block diagram illustrating an outline configuration exampleof a mobile station according to the third embodiment. The mobilestation 301 is provided with a buffer section 900, a transmission methoddetermination section 901, a first transmission signal generationsection 902, a radio section 903, a PA section 904, a transmissionantenna 905, a second transmission signal generation section 906, aradio section 907, a PA section 908, a transmission antenna 909, atransmission power headroom calculation section 910, a controlinformation transmission section 911, a control information receptionsection 912, a reception antenna 913, and a retransmission controlsection 914.

The mobile station 301 uses one transmission antenna 905 and receivesthe transmission acknowledgement signal that is control information,with the reception antenna 913, after having performed the datatransmission through the use of the non-contiguous frequency. Thecontrol information reception section 912 obtains the transmissionacknowledgement signal of ACK or NACK and control signal indicating thefrequency allocation information, the number of the transmissionantennas, and the like, from the received signal.

The control information reception section 912 inputs the transmissionacknowledgement signal to the retransmission control section 914, inputsthe information of the number of retransmission antennas to thetransmission method determination section 901, inputs the frequencyallocation information to the first transmission signal generationsection 902 and the second transmission signal generation section 906,and inputs transmission powers of the transmission antennas 905 and 909to the PA section 904 and the PA section 908, respectively. When thetransmission acknowledgement signal exhibits ACK, transmission datainput to the buffer section 900 is input to the transmission methoddetermination section 901, and, when the transmission acknowledgementsignal exhibits NACK, transmission data which has not been able to bereceived correctly in the base station 303 and which is stored in thebuffer is input to the transmission method determination section 901,for retransmission.

When the retransmission data and the number of the retransmissionantennas are input and the number of antennas is two or more, thetransmission method determination section 901 applies predeterminedtransmission diversity such as CDD (Cyclic Delay Diversity) and SFBC(Space Frequency Block Code). The first transmission signal generationsection 902 inputs the information whether or not the transmissiondiversity is applied and the retransmission data, input from thetransmission method determination section 901 and performs the sameprocessing as the processing from the coding section 101 to the CPinsertion section 108, in FIG. 1. The transmission signal isup-converted by the radio section 903, is amplified by the PA section904 based on the transmission power information, notification of whichhas been received from the control information reception section 912,and is transmitted from the transmission antenna 905.

In regard to the transmission antenna 909, in the same way as thetransmission antenna 905, the retransmission processing is performedbased on the information whether or not the transmission diversity isapplied and based on the retransmission data input from the transmissionmethod determination section 901.

The configuration of the base station 303 is the same as that of FIG. 2and determination is performed whether or not the decoding has beenperformed correctly or not, by detecting an error in the decoded resultof the received data by the CRC in the cyclic redundancy check section211. When the cyclic redundancy check section 211 has determined thatthe received data is correct, the base station 303 transmits ACK via thetransmission acknowledgement signal transmission section 218. When anerror has been detected in the received data, the base station 303transmits NACK via the transmission acknowledgement signal transmissionsection 218. Furthermore, the information such as the PH stored in thecontrol information buffer section 220 is input to the frequencyallocation decision section 214.

The frequency allocation decision section 214 determines the frequencyallocation, the number of the transmission antennas 905, and atransmission power, to be used at the time of the retransmission basedon the channel information input from the channel estimation section 213and the control information such as a PH. The frequency allocation andthe number of the transmission antennas 905 to be used at the time ofthe retransmission are transmitted as the control information via thecontrol information generation section 215 and the control informationtransmission section 216. Here, since the peak power is reduced when thetransmission method using the contiguous bands is employed at the timeof the retransmission, the required back-off amount becomes small.

When the number of antennas used in the retransmission is N_(ANT), thetransmission power per one antenna is not set as P_(TX)−Log(N_(ANT)),but may be set as P_(TX)−Log (N_(ANT))+α. However, P_(TX) is thetransmission power at the time of the initial transmission and aexpresses a back-off amount difference between the case of using thebands non-contiguously and the case of using the bands contiguously.

While in the present embodiment, explanation has been done on theassumption that the transmission diversity is CDD, a diversity methodsuch as SFBC can be applied. When SFBC is used, SFBC decoding isrequired after performing the multiplication of a weight in the channelcompensation section 207.

FIG. 10 is a diagram illustrating the retransmission processing of thethird embodiment. The mobile station 301 periodically notifies the basestation 303 of a PH as the control information (Step S301). In contrast,the base station 303 determines the transmission power of the mobilestation 301 in consideration of interference with a mobile station 301within the same cell as that of the PH, notification of which has beenreceived and notifies the mobile station 301 thereof (Step S302). Whenthe mobile station 301 performs data transmission, the base station 303transmits the control information, which includes information ofallocating the non-contiguous frequency, to the mobile station 301 (StepS303). The mobile station 301 transmits data by using the non-contiguousfrequency bands based on the received control information (Step S304).The mobile station 301 performs the data transmission by using thenon-contiguous frequency and the base station 303 detects an error inthe decoded result of the received data by the cyclic redundancy check.When an error has been detected and there is not a transmission power inthe PH, notification of which has been periodically received from themobile station 301, the base station 303 allocates the contiguous bands,designates the number of the retransmission antennas to be used for thetransmission diversity, and performs retransmission request (Step S305).Since the required back-off amount of the transmission power used forthe retransmission is reduced by the contiguous allocation, thetransmission power of all the transmission antennas 905 used for theretransmission is increased as compared with the transmission power atthe time of the initial transmission. The mobile station 301 performsthe retransmission based on the received control information (StepS306), and the base station 303 transmits ACK in return when the datahas been able to be received correctly (Step S307).

By applying the present embodiment, it is possible to suppress theincrease of the retransmission due to a shortage of the transmissionpower and to improve the cell throughput by the transmission diversityeffect, since the base station 303 changes the transmission method andthe number of the transmission antennas 905 for the retransmission inconsideration of a transmission power headroom when the base station 303has detected an error at the time of the transmission through the use ofthe non-contiguous frequency bands by the mobile station 301.

DESCRIPTION OF THE REFERENCE NUMERALS

-   100 Buffer section-   101 Coding section-   102 Modulation section-   103 DFT section-   104 Transmission data allocation section-   105 IDFT section-   106 Reference signal generation section-   107 Reference signal insertion section-   108 CP insertion section-   109 Radio section-   110 PA section-   111 Transmission antenna-   112 Transmission power headroom calculation section-   113 Control information transmission section-   114 Control information reception processing section-   115 Reception antenna-   116 Retransmission control section-   201 Reception antenna-   202 Radio section-   203 CP removal section-   204 Reference signal separation section-   205 DFT section-   206 Transmission data extraction section-   207 Channel compensation section-   208 IDFT section-   209 Demodulation section-   210 Decoding section-   211 Cyclic redundancy check section-   213 Channel estimation section-   214 Frequency allocation decision section-   215 Control information generation section-   216 Control information transmission section-   217 Buffer section-   218 transmission acknowledgement signal transmission section-   219 Transmission antenna-   220 Control information buffer section-   301 Mobile station-   303 Base station-   600 Buffer section-   601 Transmission signal generation section-   602 Antenna determination section-   603 Radio section-   604 PA section-   605 Transmission antenna-   606 Transmission power headroom calculation section-   607 Control information transmission section-   608 Control information reception section-   609 Reception antenna-   610 Retransmission control section-   900 Buffer section-   901 Transmission method determination section-   902 First transmission signal generation section-   903 Radio section-   904 PA section-   905 Transmission antenna-   906 Second transmission signal generation section-   907 Radio section-   908 PA section-   909 Transmission antenna-   910 Transmission power headroom calculation section-   911 Control information transmission section-   912 Control information reception section-   913 Reception antenna-   914 Retransmission control section

1. A base station comprising: a transmission section configured totransmit, to a mobile station, first information indicating firstcontrol information for controlling a number of transmission antennas ofthe mobile station for retransmitting transmission data with at leastsecond information indicating a retransmission request and thirdinformation indicating second control information for controllingretransmission power for retransmitting the transmission data; and aradio section configured to receive, from the mobile station, thetransmission data.
 2. The base station according to claim 1, wherein thefirst information indicates one or more transmission antennas used forretransmitting the transmission data.
 3. The base station according toclaim 1, wherein the first information indicates a coding for a transmitantenna diversity for retransmitting the transmission data.
 4. The basestation according to claim 1, wherein the transmission section isconfigured to transmit forth information indicating any one of aplurality of access methods for retransmitting the transmission data. 5.The base station according to claim 4, wherein the plurality of accessmethods are comprised of at least a first access method and a secondaccess method, the first access method allocates a plurality ofsubcarriers continuously to form a single cluster of subcarriers, andthe second access method non-continuously allocates the plurality ofsubcarriers in at least a first cluster and a second cluster where thefirst cluster includes a first portion of the plurality of subcarrierscontinuously allocated to form the first cluster and where the secondcluster includes a second portion of the plurality of subcarrierscontinuously allocated to form the second cluster.
 6. The base stationaccording to claim 5, wherein the first access method indicatesDFT-S-OFDM, and the second access method indicates Clustered DFT-S-OFDM.7. The base station according to claim 1, wherein the third informationindicates the second control information for increasing theretransmission power.
 8. The base station according to claim 1, whereinthe transmission section is configured to transmit the first informationalong with at least the second information and the third information incase of performing retransmission request to the mobile station.
 9. Amobile station comprising: a reception section configured to receive,from a base station, first information indicating first controlinformation for controlling a number of transmission antennas of themobile station for retransmitting transmission data with at least secondinformation indicating a retransmission request and third informationindicating second control information for controlling retransmissionpower for retransmitting the transmission data; and a radio sectionconfigured to transmit, to the base station, the transmission data usingone or more transmission antennas controlled using the firstinformation.
 10. The mobile station according to claim 9, wherein thefirst information indicates one or more transmission antennas used forretransmitting the transmission data.
 11. The mobile station accordingto claim 9, wherein the first information indicates a coding for atransmit antenna diversity for retransmitting the transmission data. 12.The mobile station according to claim 9, wherein the reception sectionis configured to receive forth information indicating anyone of aplurality of access methods for retransmitting the transmission data.13. The mobile station according to claim 12, wherein the plurality ofaccess methods are comprised of at least a first access method and asecond access method, the first access method allocates a plurality ofsubcarriers continuously to form a single cluster of subcarriers, andthe second access method non-continuously allocates the plurality ofsubcarriers in at least a first cluster and a second cluster where thefirst cluster includes a first portion of the plurality of subcarrierscontinuously allocated to form the first cluster and where the secondcluster includes a second portion of the plurality of subcarrierscontinuously allocated to form the second cluster.
 14. The mobilestation according to claim 13, wherein the first access method indicatesDFT-S-OFDM, and the second access method indicates Clustered DFT-S-OFDM.15. The mobile station according to claim 9, further comprising: acontrol circuit configured to control the retransmission power forretransmitting the transmission data based on the received thirdinformation.
 16. A base station comprising: a transmission sectionconfigured to transmit, to a mobile station, first informationindicating first control information for controlling a number oftransmission antennas of the mobile station for retransmitting data withat least second information indicating a retransmission request, thirdinformation indicating second control information for controllingretransmission power for retransmitting the data, the transmissionsection configured to transmit, to the mobile station, forth informationindicating any one of a plurality of access methods for retransmittingthe data, the plurality of access methods are comprised of at least afirst access method and a second access method, the first access methodallocates a plurality of subcarriers continuously to form a singlecluster of subcarriers, the second access method non-continuouslyallocates the plurality of subcarriers in at least a first cluster and asecond cluster where the first cluster includes a first portion of theplurality of subcarriers continuously allocated to form the firstcluster and where the second cluster includes a second portion of theplurality of subcarriers continuously allocated to form the secondcluster, the first access method indicates DFT-S-OFDM, and the secondaccess method indicates Clustered DFT-S-OFDM.
 17. A communication methodof a mobile station comprising: receiving, from a base station, firstinformation indicating first control information for controlling anumber of transmission antennas of the mobile station for retransmittingtransmission data with at least second information indicating aretransmission request; third information indicating second controlinformation for controlling retransmission power for retransmitting thetransmission data; and transmitting, to the base station, thetransmission data using one or more transmission antennas controlledusing the first information.